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Philip Barter - Top 30 Publications

Effect of atorvastatin, cholesterol ester transfer protein inhibition, and diabetes mellitus on circulating proprotein subtilisin kexin type 9 and lipoprotein(a) levels in patients at high cardiovascular risk.

Proprotein subtilisin kexin type 9 (PCSK9) and lipoprotein (a) [Lp(a)] levels are causative risk factors for coronary heart disease.

Association of Lipoprotein(a) With Risk of Recurrent Ischemic Events Following Acute Coronary Syndrome: Analysis of the dal-Outcomes Randomized Clinical Trial.

It is uncertain whether lipoprotein(a) [Lp(a)], which is associated with incident cardiovascular disease, is an independent risk factor for recurrent cardiovascular events after acute coronary syndrome (ACS).

Reduction of In-Stent Restenosis by Cholesteryl Ester Transfer Protein Inhibition.

Angioplasty and stent implantation, the most common treatment for atherosclerotic lesions, have a significant failure rate because of restenosis. This study asks whether increasing plasma high-density lipoprotein (HDL) levels by inhibiting cholesteryl ester transfer protein activity with the anacetrapib analog, des-fluoro-anacetrapib, prevents stent-induced neointimal hyperplasia.

Effects of age, gender and statin dose on lipid levels: Results from the VOYAGER meta-analysis database.

The effectiveness of statins in the treatment of dyslipidaemia and reduction of cardiovascular risk is well established. However, the association of statin-mediated lipid effects with age and gender is unclear. This study aimed to determine whether age and gender are associated with statin-mediated changes in low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and non-HDL-C.

Evaluation of the impact of statin therapy on the obesity paradox in patients with acute myocardial infarction: A propensity score matching analysis from the Korea Acute Myocardial Infarction Registry.

The phenomenon of obesity paradox after acute myocardial infarction (AMI) has been reported under strong recommendation of statin therapy. However, the impact of statin therapy on this paradox has not been investigated. This study investigated the impact of statin therapy on 1-year mortality according to obesity after AMI. A total of 2745 AMI patients were included from the Korea Acute Myocardial Infarction Registry after 1:4 propensity score matching analysis (n = 549 for nonstatin group and n = 2196 for statin group). Primary and secondary outcomes were all-cause and cardiac death, respectively. During 1-year follow-up, the incidence of all-cause (8.4% vs 3.7%) and cardiac (6.2% vs 2.3%) death was higher in nonstatin group than in statin (P < .001, respectively). In nonstatin group, the incidence of all-cause (7.2% vs 9.0%) and cardiac (5.5% vs 6.5%) death did not differ significantly between obese and nonobese patients. However, in statin group, obese patients had lower 1-year rate of all-cause (1.7% vs 4.8%) and cardiac (1.2% vs 2.9%) death (P < .05, respectively), and lower cumulative rates by Kaplan-Meier analysis of all-cause and cardiac death compared with nonobese patients (log-rank P < .05, respectively). The overall risk of all-cause death was significantly lower in obese than in nonobese patients only in statin group (hazard ratio: 0.35; P = .001). After adjusting for confounding factors, obesity was independently associated with decreased risk of all-cause death in statin group. In conclusion, the greater benefit of statin therapy for survival in obese patients is further confirmation of the obesity paradox after AMI.

HDL and atherosclerotic cardiovascular disease: genetic insights into complex biology.

Plasma levels of HDL cholesterol (HDL-C) predict the risk of cardiovascular disease at the epidemiological level, but a direct causal role for HDL in cardiovascular disease remains controversial. Studies in animal models and humans with rare monogenic disorders link only particular HDL-associated mechanisms with causality, including those mechanisms related to particle functionality rather than cholesterol content. Mendelian randomization studies indicate that most genetic variants that affect a range of pathways that increase plasma HDL-C levels are not usually associated with reduced risk of cardiovascular disease, with some exceptions, such as cholesteryl ester transfer protein variants. Furthermore, only a fraction of HDL-C variation has been explained by known loci from genome-wide association studies (GWAS), suggesting the existence of additional pathways and targets. Systems genetics can enhance our understanding of the spectrum of HDL pathways, particularly those pathways that involve new and non-obvious GWAS loci. Bioinformatic approaches can also define new molecular interactions inferred from both large-scale genotypic data and RNA sequencing data to reveal biologically meaningful gene modules and networks governing HDL metabolism with direct relevance to disease end points. Targeting these newly recognized causal networks might inform the development of novel therapeutic strategies to reduce the risk of cardiovascular disease.

Association of High-Density Lipoprotein-Cholesterol Versus Apolipoprotein A-I With Risk of Coronary Heart Disease: The European Prospective Investigation Into Cancer-Norfolk Prospective Population Study, the Atherosclerosis Risk in Communities Study, and the Women's Health Study.

The contribution of apolipoprotein A-I (apoA-I) to coronary heart disease (CHD) risk stratification over and above high-density lipoprotein cholesterol (HDL-C) is unclear. We studied the associations between plasma levels of HDL-C and apoA-I, either alone or combined, with risk of CHD events and cardiovascular risk factors among apparently healthy men and women.

Lipoprotein(a) and coronary atheroma progression rates during long-term high-intensity statin therapy: Insights from SATURN.

Lipoprotein(a) [Lp(a)] is a low-density lipoprotein (LDL)-like particle that associates with major adverse cardiovascular events (MACE). We examined relationships between Lp(a) measurements and changes in coronary atheroma volume following long-term maximally-intensive statin therapy in coronary artery disease patients.

Baseline Circulating FGF21 Concentrations and Increase after Fenofibrate Treatment Predict More Rapid Glycemic Progression in Type 2 Diabetes: Results from the FIELD Study.

It is not known whether circulating fibroblast growth factor 21 (FGF21) concentrations are associated with glycemic progression in patients with established type 2 diabetes. This study reports this relationship in type 2 diabetes patients participating in the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) trial.

HDL cholesterol concentration or HDL function: which matters?

Determining Glucose Metabolism Kinetics Using 18F-FDG Micro-PET/CT.

This paper describes the use of (18)F-FDG and micro-PET/CT imaging to determine in vivo glucose metabolism kinetics in mice (and is transferable to rats). Impaired uptake and metabolism of glucose in multiple organ systems due to insulin resistance is a hallmark of type 2 diabetes. The ability of this technique to extract an image-derived input function from the vena cava using an iterative deconvolution method eliminates the requirement of the collection of arterial blood samples. Fitting of tissue and vena cava time activity curves to a two-tissue, three compartment model permits the estimation of kinetic micro-parameters related to the (18)F-FDG uptake from the plasma to the intracellular space, the rate of transport from intracellular space to plasma and the rate of (18)F-FDG phosphorylation. This methodology allows for multiple measures of glucose uptake and metabolism kinetics in the context of longitudinal studies and also provides insights into the efficacy of therapeutic interventions.

Evacetrapib and Cardiovascular Outcomes in High-Risk Vascular Disease.

The cholesteryl ester transfer protein inhibitor evacetrapib substantially raises the high-density lipoprotein (HDL) cholesterol level, reduces the low-density lipoprotein (LDL) cholesterol level, and enhances cellular cholesterol efflux capacity. We sought to determine the effect of evacetrapib on major adverse cardiovascular outcomes in patients with high-risk vascular disease.

Effects of Torcetrapib and Statin Treatment on ApoC-III and Apoprotein-Defined Lipoprotein Subclasses (from the ILLUMINATE Trial).

In the ILLUMINATE Trial, treatment with the cholesteryl ester transfer protein inhibitor torcetrapib resulted in a significant increase in both atherosclerotic cardiovascular disease events and total mortality which was not explained by changes in the routinely measured plasma lipids. To determine whether alterations in lipoproteins defined by their apoprotein content that are not estimated with conventional laboratory methods contributed to these unexpected events, we measured the apoB- and apoA-containing subclasses in a subgroup of ILLUMINATE participants. We find that torcetrapib treatment significantly increased the high-density lipoprotein subclasses LpA-I and LpA-I:A-II equally (p <0.0001) and the apoC-III content of high-density lipoprotein (p <0.001) without altering the apoB-containing subclasses. In conclusion, these findings provide further evidence that the untoward effects of torcetrapib were attributable to off-target effects and not related to disturbances in lipoprotein transport.

The ATP binding cassette transporter, ABCG1, localizes to cortical actin filaments.

The ATP-binding cassette sub-family G member 1 (ABCG1) exports cellular cholesterol to high-density lipoproteins (HDL). However, a number of recent studies have suggested ABCG1 is predominantly localised to intracellular membranes. In this study, we found that ABCG1 was organized into two distinct cellular pools: one at the plasma membrane and the other associated with the endoplasmic reticulum (ER). The plasma membrane fraction was organized into filamentous structures that were associated with cortical actin filaments. Inhibition of actin polymerization resulted in complete disruption of ABCG1 filaments. Cholesterol loading of the cells increased the formation of the filamentous ABCG1, the proximity of filamentous ABCG1 to actin filaments and the diffusion rate of membrane associated ABCG1. Our findings suggest that the actin cytoskeleton plays a critical role in the plasma membrane localization of ABCG1.

Aldosterone Does Not Predict Cardiovascular Events Following Acute Coronary Syndrome in Patients Initially Without Heart Failure.

Aldosterone may have adverse effects in the myocardium and vasculature. Treatment with an aldosterone antagonist reduces cardiovascular risk in patients with acute myocardial infarction complicated by heart failure (HF) and left ventricular systolic dysfunction. However, most patients with acute coronary syndrome do not have advanced HF. Among such patients, it is unknown whether aldosterone predicts cardiovascular risk.

Erratum. Impact of Perturbed Pancreatic β-Cell Cholesterol Homeostasis on Adipose Tissue and Skeletal Muscle Metabolism. Diabetes 2016;65:3610-3620.

Treatment With Dalcetrapib Modifies the Relationship Between High-Density Lipoprotein Cholesterol and C-Reactive Protein.

Professor Philip Yu-An Ding 1949-2015.

Consensus clinical recommendations for the management of plasma lipid disorders in the Middle East.

Plasma lipid disorders are key risk factors for the development of atherosclerotic cardiovascular disease (ASCVD) and are prevalent in the Middle East, with rates increasing in recent decades. Despite this, no region-specific guidelines for managing plasma lipids exist and there is a lack of use of guidelines developed in other regions.

Impact of Perturbed Pancreatic β-Cell Cholesterol Homeostasis on Adipose Tissue and Skeletal Muscle Metabolism.

Elevated pancreatic β-cell cholesterol levels impair insulin secretion and reduce plasma insulin levels. This study establishes that low plasma insulin levels have a detrimental effect on two major insulin target tissues: adipose tissue and skeletal muscle. Mice with increased β-cell cholesterol levels were generated by conditional deletion of the ATP-binding cassette transporters, ABCA1 and ABCG1, in β-cells (β-DKO mice). Insulin secretion was impaired in these mice under basal and high-glucose conditions, and glucose disposal was shifted from skeletal muscle to adipose tissue. The β-DKO mice also had increased body fat and adipose tissue macrophage content, elevated plasma interleukin-6 and MCP-1 levels, and decreased skeletal muscle mass. They were not, however, insulin resistant. The adipose tissue expansion and reduced skeletal muscle mass, but not the systemic inflammation or increased adipose tissue macrophage content, were reversed when plasma insulin levels were normalized by insulin supplementation. These studies identify a mechanism by which perturbation of β-cell cholesterol homeostasis and impaired insulin secretion increase adiposity, reduce skeletal muscle mass, and cause systemic inflammation. They further identify β-cell dysfunction as a potential therapeutic target in people at increased risk of developing type 2 diabetes.

Variability of low-density lipoprotein cholesterol response with different doses of atorvastatin, rosuvastatin, and simvastatin: results from VOYAGER.

Patient response to statin treatment is individual and varied. As a consequence, when using a specific-dose approach, as recommended in the 2013 American College of Cardiology/American Heart Association guideline, there will be a range of reductions in the concentration of low-density lipoprotein cholesterol (LDL-C). The aim of this study was to use individual patient data from the VOYAGER meta-analysis to determine the extent of the variability in LDL-C reduction in response to treatment across the recommended doses of different statins.

Dyslipidaemia in the Middle East: Current status and a call for action.

The increase in the cardiovascular disease (CVD)-associated mortality rate in the Middle East (ME) is among the highest in the world. The aim of this article is to review the current prevalence of dyslipidaemia and known gaps in its management in the ME region, and to propose initiatives to address the burden of dyslipidaemia. Published literature on the epidemiology of dyslipidaemia in the ME region was presented and discussed at an expert meeting that provided the basis of this review article. The high prevalence of metabolic syndrome, diabetes, familial hypercholesterolaemia (FH) and consanguineous marriages, in the ME region, results in a pattern of dyslipidaemia (low high-density lipoprotein cholesterol and high triglycerides) that is different from many other regions of the world. Early prevention and control of dyslipidaemia is of paramount importance to reduce the risk of developing CVD. Education of the public and healthcare professionals and developing preventive programs, FH registries and regional guidelines on dyslipidaemia are the keys to dyslipidaemia management in the ME region.

Defining severe familial hypercholesterolaemia and the implications for clinical management: a consensus statement from the International Atherosclerosis Society Severe Familial Hypercholesterolemia Panel.

Familial hypercholesterolaemia is common in individuals who had a myocardial infarction at a young age. As many as one in 200 people could have heterozygous familial hypercholesterolaemia, and up to one in 300 000 individuals could be homozygous. The phenotypes of heterozygous and homozygous familial hypercholesterolaemia overlap considerably; the response to treatment is also heterogeneous. In this Review, we aim to define a phenotype for severe familial hypercholesterolaemia and identify people at highest risk for cardiovascular disease, based on the concentration of LDL cholesterol in blood and individuals' responsiveness to conventional lipid-lowering treatment. We assess the importance of molecular characterisation and define the role of other cardiovascular risk factors and advanced subclinical coronary atherosclerosis in risk stratification. Individuals with severe familial hypercholesterolaemia might benefit in particular from early and more aggressive cholesterol-lowering treatment (eg, with PCSK9 inhibitors). In addition to better tailored therapy, more precise characterisation of individuals with severe familial hypercholesterolaemia could improve resource use.

In vivo PET imaging with (18)FFDG to explain improved glucose uptake in an apolipoprotein A-I treated mouse model of diabetes.

Type 2 diabetes is characterised by decreased HDL levels, as well as the level of apolipoprotein A-I (apoA-I), the main apolipoprotein of HDLs. Pharmacological elevation of HDL and apoA-I levels is associated with improved glycaemic control in patients with type 2 diabetes. This is partly due to improved glucose uptake in skeletal muscle.

Effects of the BET-inhibitor, RVX-208 on the HDL lipidome and glucose metabolism in individuals with prediabetes: A randomized controlled trial.

High-density lipoprotein (HDL) and apolipoprotein A-I (apoA-I) can modulate glucose metabolism through multiple mechanisms. This study determined the effects of a novel bromodomain and extra-terminal (BET) inhibitor (RVX-208) and putative apoA-I inducer on lipid species contained within HDL (HDL lipidome) and glucose metabolism.

Coronary artery disease: Scavenger receptor class B1--a target to reduce CHD risk?

New Era of Lipid-Lowering Drugs.

There are several established lipid-modifying agents, including statins, fibrates, niacin, and ezetimibe, that have been shown in randomized clinical outcome trials to reduce the risk of having an atherosclerotic cardiovascular event. However, in many people, the risk of having an event remains unacceptably high despite treatment with these established agents. This has stimulated the search for new therapies designed to reduce residual cardiovascular risk. New approaches that target atherogenic lipoproteins include: 1) inhibition of proprotein convertase subtilisin/kexin type 9 to increase removal of atherogenic lipoproteins from plasma; 2) inhibition of the synthesis of apolipoprotein (apo) B, the main protein component of atherogenic lipoproteins; 3) inhibition of microsomal triglyceride transfer protein to block the formation of atherogenic lipoproteins; 4) inhibition of adenosine triphosphate citrate lyase to inhibit the synthesis of cholesterol; 5) inhibition of the synthesis of lipoprotein(a), a factor known to cause atherosclerosis; 6) inhibition of apoC-III to reduce triglyceride-rich lipoproteins and to enhance high-density lipoprotein (HDL) functionality; and 7) inhibition of cholesteryl ester transfer protein, which not only reduces the concentration of atherogenic lipoproteins but also increases the level and function of the potentially antiatherogenic HDL fraction. Other new therapies that specifically target HDLs include infusions of reconstituted HDLs, HDL delipidation, and infusions of apoA-I mimetic peptides that mimic some of the functions of HDLs. This review describes the scientific basis and rationale for developing these new therapies and provides a brief summary of established therapies.

A VOYAGER Meta-Analysis of the Impact of Statin Therapy on Low-Density Lipoprotein Cholesterol and Triglyceride Levels in Patients With Hypertriglyceridemia.

Elevated triglyceride (TG) levels are associated with increased cardiovascular disease risk. In patients with mild-to-moderate hypertriglyceridemia, defined by the European Atherosclerosis Society Consensus Panel as a TG level of 177 to 885 mg/dl (2.0 to 10.0 mmol/L), low-density lipoprotein cholesterol (LDL-C) reduction remains the primary treatment goal. Using data from the indiVidual patient meta-analysis Of statin therapY in At risk Groups: Effects of Rosuvastatin, atorvastatin and simvastatin (VOYAGER) meta-analysis, we analyzed LDL-C and TG reductions in patients with baseline TG ≥177 mg/dl (≥2.0 mmol/L). Least squares mean percentage change from baseline in LDL-C and TG was compared using 15,800 patient exposures to rosuvastatin 5 to 40 mg, atorvastatin 10 to 80 mg, and simvastatin 10 to 80 mg in patients with baseline TG ≥177 mg/dl (≥2.0 mmol/L). Comparisons were made using mixed-effects models with data only from studies directly comparing treatments by randomized design. Mean LDL-C reductions ranged from -26.9% to -55.5%. Rosuvastatin 10 to 40 mg resulted in significantly greater LDL-C reductions than equal or double doses of atorvastatin and simvastatin (p <0.05). Mean TG reductions ranged from -15.1% to -31.3%. Rosuvastatin 10 mg resulted in significantly greater TG reductions than atorvastatin 10 mg (p <0.05). Rosuvastatin 20 and 40 mg resulted in TG reductions similar to those with equal doses of atorvastatin. Rosuvastatin 10 to 40 mg resulted in significantly greater TG reductions than equal or double doses of simvastatin (p <0.05). In conclusion, in patients with hypertriglyceridemia, LDL-C reduction was substantial and dependent on the choice and dose of statin. TG reduction was numerically less than for LDL-C, and additional TG-lowering therapy may be considered to further reduce residual cardiovascular risk.

Inhibition of inflammatory signaling pathways in 3T3-L1 adipocytes by apolipoprotein A-I.

Activation of inflammatory signaling pathways links obesity with metabolic disorders. TLR4-mediated activation of MAPKs and NF-κB are 2 such pathways implicated in obesity-induced inflammation. Apolipoprotein A-I (apoA-I) exerts anti-inflammatory effects on adipocytes by effluxing cholesterol from the cells via the ATP binding cassette transporter A1 (ABCA1). It is not known if these effects involve inhibition of inflammatory signaling pathways by apoA-I. This study asks if apoA-I inhibits activation of MAPKs and NF-κB in mouse 3T3-L1 adipocytes and whether this inhibition is ABCA1 dependent. Incubation of differentiated 3T3-L1 adipocytes with apoA-I decreased cell surface expression of TLR4 by 16 ± 2% and synthesis of the TLR4 adaptor protein, myeloid differentiation primary response 88, by 24 ± 4% in an ABCA1-dependent manner. ApoA-I also inhibited downstream activation of MAPKs, such as ERK, p38MAPK, and JNK, as well as expression of proinflammatory adipokines in bacterial LPS-stimulated 3T3-L1 adipocytes in an ABCA1-dependent manner. ApoA-I, by contrast, suppressed nuclear localization of the p65 subunit of NF-κB by 30 ± 3% in LPS-stimulated 3T3-L1 adipocytes in an ABCA1-independent manner. In conclusion, apoA-I inhibits TLR4-mediated inflammatory signaling pathways in adipocytes by preventing MAPK and NF-κB activation.-Sultana, A., Cochran, B. J., Tabet, F., Patel, M., Cuesta Torres, L., Barter, P. J., Rye, K.-A. Inhibition of inflammatory signaling pathways in 3T3-L1 adipocytes by apolipoprotein A-I.

High-Density Lipoprotein-Associated miR-223 Is Altered after Diet-Induced Weight Loss in Overweight and Obese Males.

microRNAs (miRNAs) are small, endogenous non-coding RNAs that regulate metabolic processes, including obesity. The levels of circulating miRNAs are affected by metabolic changes in obesity, as well as in diet-induced weight loss. Circulating miRNAs are transported by high-density lipoproteins (HDL) but the regulation of HDL-associated miRNAs after diet-induced weight loss has not been studied. We aim to determine if HDL-associated miR-16, miR-17, miR-126, miR-222 and miR-223 levels are altered by diet-induced weight loss in overweight and obese males.